Optical waveguide (passive/active) is basic building blocks for high-speed on-chip optical interconnect devices. A core-size and cross-sectional geometry of the waveguide plays vital role in terms of light coupling efficiency, dispersion, nonlinear interactions and polarization dependencies. Nevertheless, higher refractive index contrast between core and cladding of a silicon-on-insulator (SOI) based waveguides facilitates a realization of ultra-compact photonics device structures resulting into large scale integration and multifunctional integrated optoelectronic chip (IOC).
However, challenges associated with small cross-section waveguides (microns to sub-micron) are the uniformity over large propagation lengths (ranging from few tens of micro-meter to few millimeters), core-cladding interface roughness and overall fabrication reproducibility.
Therefore, various post-fabrication trimming techniques have been proposed to compensate phase errors resulting out of process related uncertainties and non-uniformities in waveguide dimensions. Some attractive local refractive index trimming techniques have been reported during the post-fabrication treatments to detune the wavelength dependent characteristics of waveguide device. However, the local refractive index trimming techniques can not modify the dimensions of the waveguide during a design phase.